Controlled gas packaging

ABSTRACT

A method and apparatus for controlled or modified atmosphere packaging of products such as foodstuffs, whereby the product ( 17 ) is weighed prior to or in the packaging machine and regulating the amount of gas inserted into the package in proportion to the weight of the product. User controlled variables may be used to determine the amount of gas to be injected into a package for a given weight or size of package, typically 1.5 to 1.75 liters of Carbon Dioxide per Kg of meat cut depending upon the type of meat, number/size of voids and bag size.

FIELD OF INVENTION

[0001] This invention relates to method and apparatus for packaging, andhas particular application to the packaging of spoilable materials, e.g.foodstuffs, and in particular meat cuts in a controlled or modifiedatmosphere bag.

BACKGROUND

[0002] Previous methods of packaging spoilable material have involvedpacking the product within a plastic bag or the like, evacuating thebag, then injecting a standard amount of gas or gas mixture in place ofthe air. This is sometimes called “controlled atmosphere packaging” or“modified atmosphere packaging”. One example of such machines is ourCaptech machine described in U.S. Pat. No. 4,926,614. Prior art machinesrequired operators to inspect the product prior to gas injection. Insome cases a small pack could be overfilled with injected gas leading toballooning or bursting of the bag. In other cases the bag would beunderfilled, resulting in crushing of the pack when the gas was absorbedby the meat.

OBJECT

[0003] It is an object of this invention to provide an improvedpackaging method and/or apparatus, or one, which will at least providethe food industry with a useful choice.

STATEMENT OF INVENTION

[0004] In one aspect the invention provides a method of controlling theamount of gas injected into a package by determining the weight of theproduct, and automatically varying the amount of gas injected inproportion to the weight of the product.

[0005] Preferably the method involves setting a user determined variableto regulate the desired amount of gas per weight or type of product, andcombining this setting with the weight of the product, which preferablyis automatically weighed in the packaging machine or prior to theproduct reaching the packaging machine.

[0006] In another aspect the invention provides apparatus for controlledor modified atmosphere packaging of products, including: means forweighing a product to be packaged; means for insertion of a product intoa package; means for evacuating the package; means for injecting a gasinto the package; means for regulating the amount of gas injected basedon information on the weight of product from the weighing means andmeans for sending the package.

[0007] Preferably the weighing means provides an output to a controldevice such as microprocessor which in turn can be used to control theamount of gas injected into the package.

[0008] Preferably the weighing means is closely associated with theapparatus. In one version of the invention, the weighing means can formpart of the packaging machine, and in another aspect, the weighing meanscan be a weigh station situated prior to the packaging machine, morepreferably its forms part of a conveyor conveying product to thepackaging machine so that the weight of the product is determined beforethe product reaches the packaging machine.

[0009] Preferably the packaging machine has provision to enable the userto set the amount of gas per weight of product, as the user may wish tovary the amount of gas per weight of product depending upon type ofproduct, its capability of absorbing the injected gas, the number andtype of voids associated with the product, the size of the bag, or thephysical size or shape of the product.

[0010] By way of example, the packaging of meat there is an industry“rule of thumb” that lamb or beef cuts will absorb about one liter ofcarbon dioxide per kilogram of meat. Based on this figure, some MeatProcessors prefer to inject about 1.5 liters of carbon dioxide perkilogram of meat, while some may prefer to set their machine to attemptto insert 1.75 liters of carbon dioxide per kilogram of meat. It isdifficult to ensure the meat cuts are precisely the same weight, and forexample a meat pack intended to contain 10 kg of meat on average, maycontain anywhere between 8 kg-11.5 kg of meat.

DRAWINGS

[0011] These and other aspects, which should be considered in all itsnovel aspects will become apparent from the following description, whichis given by way of example only, with reference to the accompanyingdrawings, in which:

[0012]FIG. 1 illustrates a schematic view of a preferred packagingapparatus.

[0013]FIG. 2 illustrates a top plan view of conveyor and gas fillingmachine.

[0014]FIG. 3 illustrates a front elevation of the conveyor andgas-filling machine of FIG. 2.

[0015] In example 1 the weighing means can be part of the chamber, butin the case of example 2 the weighing means can be situated prior to thechamber.

EXAMPLE 1 Weighing Means

[0016] In this example weighing of the product to be packaged can takeplace as the product enters the chamber—preferably before evacuationtakes place. A weigh scale 12A can be situated on or form part of thebase 12 of the chamber. Information on the weight of the product canthen be used to automatically adjust the amount of gas to be injectedinto the package—see below.

[0017] By way of example we use a chamber 10 defined by a removablecover 11 and a base 12, although any other type of gas flushingapparatus can be used with this inventive concept.

[0018] Gas passages are provided, connecting the apparatus to a vacuumsource 23 and one or more gas sources 24. One passage 25 includes asnorkel 13 intended for connection with a container held in the chamber10, as detailed below, and a second passage 14 provides access to thechamber 10 itself. In some applications, it may be desirable to providepairs of passageways, one connected to the vacuum source and one to agas source. Alternatively, as shown single passageways may be used withappropriate valves to switch the passageway between the two functions.

[0019] Preferably the chamber 10 is of a size able to comfortablyaccommodate a box 15 and heat sealable bag 16 with its contents 17.

[0020] In its preferred form the apparatus includes clamping and sealingapparatus for the bag 16, inside the chamber 10, separate andindependently movable from the cover 11. This apparatus includesclamping bars 18 mounted around the snorkel 13 for temporarily clampingthe mouth of the bag around the snorkel 13, and sealing bars 19positioned beyond the snorkel 13 for sealing the mouth of bag 16 betweenthe snorkel and the product 17.

[0021] One or both sealing bars 19 are movable, preferably by the use ofa pneumatic cylinder 20, such that the mouth of the bag can be left openor sealed shut between the snorkel 13 and the product 17. The upperclamping bar 18 and sealing bar 19 can be mounted on a pivotable jaw 21with a handle 22 by which it may be moved up or down. All this apparatusis contained in the chamber 10 along with the product 17 and itspackaging, and is covered by the lid 11. An airtight seal is formedbetween the lid 11 and the base 12 in normal use.

[0022] It is preferable for the clamping bars 18 to be positioned behindthe sealing bars 19 as shown, rather than in front of them. If theclamping bars 18 were positioned in front of the sealing bars 19 withthe snorkel 13 protruding through them, it would be necessary towithdraw the snorkel before sealing the bag, and furthermore a smallpocket of air would inevitably be trapped between the clamping bars andthe seal, and would be released into the bag upon removal of theclamping bars. With the arrangement of the present invention the snorkelis not required to move, and there is no air entrapment at the mouth ofthe bag.

[0023] In use, the product 17 to be packed is placed within a heatsealable bag 16 and box 15, and is then placed within the chamber 10.The chamber has appropriate seals about its edge, so that the chamberitself can be evacuated as well as the bag. The bag is placed within thechamber 10 and the mouth of the bag 16 fitted over the snorkel 13. Thebag is then clamped off across the snorkel with the pair of clamp bars18.

Evacuation

[0024] The chamber 10 and the bag 16 are evacuated, preferablysimultaneously, so that the bag is completely emptied. By controllingthe pressure within the chamber as the bag is evacuated, the bag can becontrolled so that it does not collapse too soon, cutting offcommunication between contents and the snorkel 13. Preferably both thechamber and the bag are evacuated from the same source, but the snorkel13 is narrower than the passageway 14. This means that the chamber isevacuated faster than the bag, and the bag expands inside the chamber asit is emptied, rather than collapsing. This prevents air being trappedin pockets in the bag. Alternatively, the bag and the chamber could beevacuated at the same rate. Even if the bag empties slightly faster thanthe chamber and collapses as a result, the difference between the airpressure in the bag and the air pressure around it will not be greatenough to trap air inside.

[0025] When a desired vacuum level in the chamber is achieved, a vacuumpressure switch 26 stops the evacuation and holds the chamber at thatvacuum level. The evacuation of the bag continues through the nozzle 13,and the bag collapses as a result. When the desired vacuum level in thebag is reached a second pressure switch 27 is activated. The chamber andthe bag are then refilled. The use of pressure switches to turn thesystem on and off allows the vacuum level to be accurately determinedand achieved without undue stress being put on the bag in the process.By using the same vacuum source to evacuate both chamber and bag it iseasy to avoid having any great difference between the pressures in each.

[0026] To speed up the last stages of evacuation of the bag, it may befound desirable to refill the chamber slightly after activation of thefirst pressure switch and initial collapse of the bag, to put greaterpressure on the bag and squeeze the last of the air out. Such collapsingof the bag could result in entrapment of air, but because the bag isalready substantially evacuated at this stage this will in general notbe a problem.

[0027] This system also allows visual checking, in that the bag can beseen to inflate and collapse within the chamber (given one or morewindows in the chamber lid or walls) at different times in the process.If, for example, the proper vacuum is not achieved in the bag for anyreason, it will not collapse even if a partial reduction of pressure hasoccurred, because the internal pressure will still be greater than thatin the chamber.

Gas Filling

[0028] When the bag is fully empty, or as empty as the vacuum pump canmake it within the desired cycle time, the chamber and the bag arerefilled, preferably at the same rate. This time the bag is filled witha selected gas or gas mixture introduced through the nozzle 13. In thecase of packaging meat the gas is commonly carbon dioxide, althoughother gases or gas mixtures may be used. Depending upon the nature ofthe contents of the bag other gas mixtures may be used to control thestorage, ripening, or other qualities of the item stored within the bag.

[0029] While the bag is being filled with a gas or gas mixture, thechamber is also filled, most conveniently with air, although other gasescould be used. By filling the chamber at a controlled rate at the sametime as filling the bag, it is possible to balance the pressure betweenthe gas within the bag, and the air within the chamber. This allows thebag to be filled accurately with a metered quantity of gas, and alsoavoids undue pressure being placed on the bag.

[0030] The amount of gas injected into the bag can be controlled by themicroprocessor, which determines the amount of gas based on the usersettings and the weight of the product. For example, one meat processormay wish to achieve set rates of 1.5 liters of Carbon Dioxide per Kg ofmeat cuts, whilst another may prefer to achieve fill volumes of 1.7liters of Carbon Dioxide per Kg of meat cuts. By entering the requiredsettings the machine can calculate the required amount of gas based onthe weight of the product. This has not been possible in prior artequipment where the average pack size may be for example 10 kg but packsmay range in size from 8 kg to 11.5 kg for example.

[0031] When atmospheric pressure has been reached in the chamber, thecover 11 of the chamber can be removed, and the sealing bars 19 broughttogether to seal the bag 16. If two chambers are used together, thecover 11 can be shifted to the second chamber at this stage, andevacuation of another bag commenced while the first is being sealed.When the bag is sealed, the clamping bars 18 can be released and the bagremoved from the chamber.

[0032] This example has the advantage that the bag can be well evacuatedto leave a very low amount of residual air, and then accurately filledwith a known quantity of gas, and avoids the disadvantages of priorvacuum packaging methods in which the bag is exposed to atmosphericpressure during the vacuum and gas flushing operations. It also has theadvantage that only the bag is filled with the required amount of gascalculated on the weight of the product and any user settings, and nogas is allowed to escape into the chamber. It is also believed that thebags are less likely to be damaged in the operation as there can belittle or no stress on the bag during filling.

EXAMPLE 2

[0033] In this example, any type of packaging machine can be used, andfor example it may be a packaging machine 10 of the type illustrated anddescribed with reference to FIG. 1, so that the product can be insertedinto a package, the package evacuated and then gas filled to provide acontrolled atmosphere prior to sealing of the bag. (Except that theweigh station 12A is replaced by external weigh station 54 situatedprior to the product reaching the packaging machine).

[0034]FIGS. 2 and 3 show the use of such as machine, in association withan indexing in feed conveyor 50 and an output conveyor 51.

[0035] Preferably the indexing in feed conveyor has an associated weightstation 54 situated beneath the conveyor belt so that the product isweighed just before it enters the packaging machine.

[0036] Information on the way the product can be feed to themicroprocessor (not shown here but represented by numeral 30 in FIG. 1)which in turn controls the evacuation of the bag and the amount of gasinjected, once the bag has been evacuated.

ADVANTAGES

[0037] By this means it is possible to more accurately determine theamount of gas to be inserted into the bag, based on the weight of theproduct.

[0038] This has the advantage that a production line can pack the meatpacks, and fill them with the required amount of gas more accurately,and at a faster rate than conventional controlled atmosphere packaginglines. Conventional lines require the operator to visually inspect, andin some cases to manually adjust the amount of gas per package based onthe visual indication of the size of the package. This slows down theprocess, and unless the operator is extremely careful, will result inthe ballooning or bursting of some packages where excess gas is injectedinto a smaller pack size, or too little gas is injected into a packresulting in the absorption of the gas into the meat during transport,and subsequent crushing of the package. In neither case the end resultis acceptable.

[0039] Whilst it is possible to regulate the amount of gas preciselybased on the exact weight of the package, we prefer to determine anumber of weight bands for example, 8-8.5 kg, 8.5-9 kg, 9-9.5 kg, 9.5-10kg, 10-10.5 kg, 10.5-11 kg, 11-11.5 kg and 11.5-12 kg and to determineif the weight of the package falls within one of these bands, and thento inject a predetermined amount of gas into the package in proportionto the amount specified for that particular weight band. In addition thegas to be injected can be varied depending upon the type of product, thetransit time from packing to retail display and purchased by theconsumer. In some cases we prefer to inject both carbon dioxide andnitrogen, so that the amount of gas can be controlled carefully,allowing the carbon dioxide to be absorbed by the meat during transport,whilst the nitrogen remains as a buffer gas preventing crushing of thepackage (which would be the case if only carbon dioxide was present andit was fully absorbed by the meat).

[0040] By setting the parameter relating to the type of product to bepacked (for example ground beef which has a greater surface area than ameat cut) and then using the automatic weighing, and automaticregulation of the gas to be injected in proportion to the information ona package weight, it is possible to greatly speed up the controlledatmosphere packing of food products (and in particular meat) whilst atthe same time minimising the risk of damage or spoilage to the product.

VARIATIONS

[0041] Whilst it is preferred the weighing of the product occurs in thechamber as in example 1, or shortly prior to the chamber by having aweigh station associated with the indexing and feed conveyor 50, it ispossible to weigh the combined package or their contents separately,some distance from the machine, for example when the meat cuts have beenprepared, and then transmit this information to the microprocessor. Ineither event the total package weight (or the aggregate weight of theindividual meat cuts making up that package will be fed to themicroprocessor so that the required amount of gas can be injectedautomatically.

[0042] Finally, it will be appreciated that various alterations ormodifications maybe made to the foregoing without departing from thescope of this invention.

We claim:
 1. Apparatus for controlled or modified atmosphere packagingof products, including means for weighing a product to be packaged;means for insertion of a product into a package; means for evacuatingthe package; means for injecting a gas into the package; means forregulating the amount of gas injected based on information on the weightof product from the weighing means and means for sending the package. 2.Apparatus as claimed in claim 1, wherein the weighing means provides anoutput to a control device such as microprocessor which in turn can beused to control the amount of gas injected into the package. 3.Apparatus as claimed in claim 1, wherein the weighing means forms partof the packaging machine.
 4. Apparatus as claimed in claim 1, whereinthe weighing means is a weigh station situated prior to the packagingmachine.
 5. Apparatus as claimed in claim 1, wherein the weighing meansis closely associated with the apparatus.
 6. Apparatus as claimed inclaim 1, wherein the weighing means is associated with a conveyorconveying product to the packaging machine so that the weight of theproduct is determined before the product reaches the packaging machine.7. Apparatus as claimed in claim 1, wherein the packaging machine has amanual control to enable the user to set the amount of gas per weight ortype of product.
 8. A method of controlling the amount of gas injectedinto a package by determining the weight or type of product, andautomatically varying the amount of gas injected based on the weight ofthe product.
 9. A method as claimed in claim 8, wherein the methodinvolves setting a user determined variable to regulate the desiredamount of gas per weight of product, and combining this setting with theweight of the product.